Final Report for "Toward Quantifying Kinetics of Biotic and Abiotic Metal Reduction with Electrical Geophysical Methods" DE-FG02-08ER64520
Although changes in the bulk electrical conductivity in aquifers have been attributed to microbial activity, electrical conductivity has never been used to infer biogeochemical reaction rates quantitatively. To explore the use of electrical conductivity to measure reaction rates, we conducted iron oxide reduction experiments of increasing biological complexity. To quantify reaction rates, we proposed composite reactions that incorporated the stiochiometry of five different types of reactions: redox, acid-based, sorption, dissolution/precipitation, and biosynthesis. In batch and column experiments, such reaction stiochiometries inferred from a few chemical measurements allowed quantification of the Fe-oxide reduction rate based on changes in electrical conductivity. The relationship between electrical conductivity and fluid chemistry did not hold during the latter stages of the column experiment when electrical conductivity increased while fluid chemistry remained constant. Growth of an electrically conductive biofilm could explain this late stage electrical conductivity increase. This work demonstrates that measurements of electrical conductivity and flow rate, combined with a few direct chemical measurements, can be used to quantify biogeochemical reaction rates in controlled laboratory situations and may be able to detect the presence of biofilms.
- Research Organization:
- The Pennsylvania State University, University Park, PA
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- DOE Contract Number:
- FG02-08ER64520
- OSTI ID:
- 1042448
- Report Number(s):
- DOE/FG/64520-F
- Country of Publication:
- United States
- Language:
- English
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